Production of motor or aviation fuels



June 3, 1947. D. A. HwEs l 2,421,619

PRODUCTION OF MOTOR OR AVIATION FUELS Filed Feb. 11, 1942 INVENTOR:

00A/ALD /IL BERT HWES ATTORNEYS'.

Patented June 3, 1947 PRODUCTION OF MOTOR on AVIATION FUELS Donald Albert Howes, Sunbury-on-Thames, England, assignor to Anglo-Iranian Oil Company Limited, London, England, a British jointstock corporation Application February 11, 1942, Serial No. 430,331

In Great Britain February 7, 1941 4 claims. (o1. 26o-63315) This invention relates to a process for the production of high grade motor or aviation fuels or motor or aviation fuel constituents.

It is among the objects of the present invention to produce high quality motor or aviation spirits or constituents thereof from feed stocks consisting essentially of Oleiine hydrocarbons having 4 carbon atoms in the molecule, derived for example from processes of crude oil distillation and stabilisation and from cracking operations.

A well known process for converting such materials containing isobutylene into a motor spirit or a motor spirit constituent is the so-called cold acid polymerisation process in which the C4 fraction containing isobutylene is contacted with sulphuric acid. This well known process is ac-` cording to the invention employed in the use of sulphuric acid of 55-65% strength at 0-40 C. by treatment of a C4 fraction containing isobutylene in an absorption stage carried out in the liquid phase, the temperature of the acid and the material to be treated being first reduced by cooling before admixture and maintained low by cooling the mixture in the course of the treatment, whereby the temperature is not allowed to exceed 40 C., the treatment in the rst stage continuing until the specic gravity of the acid liquor has been reduced to a degree substantially short of that at which the total water content of. the acid has been used, the acid liquor produced being on settlement and separation therefrom subjected to heat in a polymerisation stage to yield a crude mixture of diisobutylene and triisobutylene which separates as a supernatant layer, traces of acid being then removed from the crude mixture and the acid free product being then removed from the crude mixture. In this manner the isobutylene in the C4 fraction is absorbed by the sulphuric acid with the formation of acid-soluble tertiary butyl alcohol. The acid layer is separated from the unreacted C4 fraction and then heated to a temperature of about 150 C.-200 C. under such conditions that the tertiary butyl alcohol undergoes polymerisation or chemical change into a mixture of diiso butylene and triisobutylene which is withdrawn from the system. This mixture of diisobtuylene and triisobutylene is a valuable motor spirit component because'of its high octane number, which varies from 82 to 88, and may be converted into a valuable aviation spirit component by simple hydrogenation saturation carried out under pressure of from 500 to 3500 lbs. per square inch in the presence of hydrogen and in the use of freshly reduced ferrie oxide as catalyst; or as described in the specification of the copending application Serial No. 419,128, dated November 14, 1941, whereby the mixture of diisobutylene and triisobutylene is contacted with a hydrogenation 2 catalyst at a temperature within the range of 300 F.600 F. and under pressure ofirom 10-100 atmospheres in the presence of hydrogen.

While this process is effective, the possible yield of high octane number products is low because most C4 fractions obtained from cracking operations contain not more than 25% isobutylene at the most, and generally not more than 15%. An increased yield may be secured by the use of the hot acid polymerisation process in which sulphuric acid of about 7 0% strength is used at about C., or by the 'use of the catalytic 4polymerisation process, both of which effect the co-polymerisation of both isobutylene and normal butylenes; but in both of these cases the polymer spirits obtained have octane numbers lower than those of diisobutylene and triisobutylene and give, on hydrogenation saturated products of lower' octane numbers.

According to the present invention substantially complete conversion of the isobutylene content of C4 fractions to isooctane of 99-1001octane number is effected by rst subjecting the fractions to cold acid polymerisation as hereinbefore described to produce a mixture of diisobutylene and triisobutylene, the unreacted hydrocarbons being then treated for the isomerisation of the normal butylene content to isobutylene, whereupon the product is then polymerised in a further stage and the polymerisation product in common with the said mixture subjected to hydrogenation and advantageously fractionation.

The unreacted hydrocarbons from the second stage polymerisation may be re-cycled for isomerisation of any remaining normal butylene to isobutylene.

The unreacted hydrocarbons finally leaving the second polymerisation stagemay be de-hydrogenated and fractionated to yield a product that may be passed to the first polymerisation stage.

The following is an example of the application of the invention, described with reference to the accompanying diagrammatic drawing:

C4 fractions obtained, for example from cracking operations and containing both isobutylene and normal butylenes are pumped from the feed tank a, by the pump b to a conventional cold-acid polymerisation equipment c. From the equipment c two product streams emerge, namely unreacted C4 hydrocarbons comprising essentially normal butylenes and saturated isobutane and normal butane through the line l and polymerised products through the line fi, that consist essentially of diisobutylene and triisobutylene. The unreacted C4 hydrocarbons .are then processed through isomerisation equipment d, in

which the normal butylene content is isomerized to isobutylene, for example, in the manner described in the specification of co-pending appli- 1 3 cation Serial No. 413,328, dated October 2, 1941, by contacting the unreacted hydrocarbons referred to, at a temperature Within the range 300 C.-500 C. With a catalyst obtained by a combination of compounds of aluminium, -such v as the oxide or the hydrated oxide, with hydrated silica, such as silica gel artificially impregnated with alumina. The isobutyleneeproduced-is converted to a further quantityof diisobutylene and triisobutylene in the equipment e, which is of the same type as the equipment c. The mixture of diisobutylene and triisobutylene leaves .through the line 71. The pipe lines j and 71 are connected and lead to the storage tank f, from Which ythe diisobutylene-triisobutylene mixture is passed to the hydrogenation unit g, in which, for example as describedin the specication of co-pending application Serial No. 419,128, it is contacted with a'hydrogenating-catalyst or catalysts at a temperature `Within the range 300.F.600 F. `and under a `pressure of-10-100 atmospheres inthe presence of hydrogen, whereby it is converted into -a mixture voi -isoctane and isomeric dodecanes, `which is separated in theffractionation column .h into its component fractions.

xA portion of the unreacted C4 fraction 4leaving the cold acid polymerisationequipment e may be re-cycled by the pump. z'to the isomerisation l equipmentd, so vthat any unconverted .normal passed .to a fractionating column 1c, in which hydrocarbons lighter than C4, .and .hydrogen are separated, While `the converted C4 fraction is passed to the main ,feed tank a, for recycling through the sequence of operations described. In .this manner substantially complete conversion of `Crhydrocarbons. to `isoctane and isododecane is achieved. i

.C4 hydrocarbon mixtures .not containing isobutylene or normal butylenes may be admitted through the line o into the de-hydrogenation unit n.

I claim:

1. `A processfor the production .of .a high grade motor or aviation Afuel .or constituent from C4 hydrocarbons containing olei'ines, such as are derived from the distillation and stabilization of crude oil and from cracking operations, consisting in subjecting the hydrocarbons to cold acid polymerisation. in a preliminary liquid phase absorption -stage carried out. at a low temperature at abouti-.40 C., in which stage the hydrocarbons and sulphuric acid of 55-65%,strength are cooled beforefadmixtureand maintained cool during reaction, the absorption continuing until the specic 4gravity oi the acid liquor has been reduced toa degree substantially short of that at which the total Water content of the acid hasbeen used, the Visobutylene being Iabsorbed by the acid With the formation of tertiary butyl alcohol, whereby on settlement an acid layer then separates from a supernatant layer of the .unreacted hydrocarbons, whereupon the acid liquor is heated at a temperature of about ,15G-200 C. whereby the 41 tertiary butyl Aalcohol is polymerized into a mixture of diisobutylene and triisobutylene; treating the unreacted hydrocarbons for isomerization of their normal butylene content to isobutylene;

-`[subjecting the isomerization products to polymerization in a further polymerization stage and under the same conditions of cold acid polymerization specified, for the production of a further `mixture of diisobutylene and triisobutylene; and,

subjecting 'the mixtures of diisobutylene and triisobutylene derived from both stages of cold acid .polymerization to hydrogenation.

2. A process for the production oi a high grade motor or aviation fuel or constituent as speciiied in claim l, including the step of subjecting the hydrogen saturated products to fractionation' to yield-isooctane and isododecanes.

3. A process for `the production oa high grade motor or aviation fuel or 'constituent according to claim 1, including the steps-.of recycling -a portion of the unreacted hydrocarbons leaving'fsecond cold acid, polymerization stage referred-to, to the isomerization stage Vfor isomerizationiof the'unconverted normal .butylene content .and

subjecting theremainder of the unreacted :hydrocarbons comprising a mixture of normal butane and isobutane to v dehydrogenation for conversion into a mixture of normal butylene and .isobutylene. 4. A process for the `production of a highgrade motor or avi-ation fuel or constituentv according to claim 1, including the steps of recycling -a'portion vof the unreacted hydrocarbons leaving-.the second cold acid polymerization stage to the isomerization stage for isomerizationof unconverted normal -butylene and subjecting .the remainder to dehydrogenation whereby `unreacted butane and isobutane are dehydrogenated intoa mixture containing normal butylene and yisobutylene; passing said mixture to a fractionation. stage from which hydrogen and hydrocarbons-lighter than C4 hydrocarbonsiare separated; Yand,.recycling the converted hydrocarbons comprisingbutyleneiand isobutylene with the feedstock.

DONALD ALBERTiIOWES REFERENCES CTED UNITED STATES PATENTS are of record -inf the Date Number Name 2,206,376 Vlugter July 2, -1940 2,216,285 Thomas et al Oct. 1, 1940 2,259,862 Ruys etfal. -.Oct.'21,11-941 2,171,928 Gage Sept. ,'5, y1939 2,178,808 Rosen Nov. 7,1939 2,199,132 Hull Apr: 30, 1940 2,199,133 Marschner Apr. 30, 1940 2,227,639 Frey i Jan. 7, 1941 2,263,026 Arveson Nov. 18,.-1941 2,281,804 Ruthruff May ,5, v19.42

FOREIGN PATENTS Number Country Date 470,081 Great Britain Aug..9, .1937

OTHER REFERENCES 

